The invention relates to a process for producing an open-end spinning rotor having a rotor disk made of steel which has a fiber sliding wall expanding conically from an open side to a fiber collecting groove. The fiber sliding wall and the fiber collecting groove are provided with a coating which improves the spinning characteristics.
In order to improve the operating characteristics of an open-end spinning rotor, it is known (German Published Unexamined Patent Application No. 33 39 852) to subject the entire interior surface of the spinning rotor to a boron treatment before the coating is applied that improves the spinning conditions. For this boron treatment, the whole interior space of the rotor disk is filled out with a boron treatment powder. For the layer which improves the spinning conditions, it is known to use a chemically applied nickel coating, in which particles are embedded. The grain size of the particles is approximately 4 .mu.m, and the particles are particularly diamond particles. In practice, it was found that these spinning rotors that were subjected to a boron treatment before the application of the coating that improves the spinning conditions have not had the expected results. In particular, problems have occurred when applying the coating which improves the spinning conditions.
An object of the present invention is to provide an open-end spinning rotor that facilitates the application of a layer improving the spinning characteristics such that the completed rotor meets all expectations with respect to the spinning characteristics and reduced wear.
This object and other objects are achieved by providing a process for applying a layer improving the spinning characteristics in which the boron treatment agent is applied only in the area of the fiber collecting groove prior to applying the spinning improvement layer.
In the spinning rotor construction of the present invention, the coating which improves the spinning conditions can be applied with superior results. The invention is based on the recognition that the cause of the defects in the coating of prior known spinning rotors were microcracks in the area of the fiber sliding surface that had been previously subjected to the boron treatment. Surprisingly, it was found that microcracks of this type, after the boron treatment, were not present in the fiber collecting groove. As a result of the further recognition that the boron treatment and the resulting endeavored increase of wear is not that necessary in the area of the fiber sliding surface, the solution according to the present invention was found.
According to advantageous features of certain preferred embodiments of the invention, it is provided that, before a boron treatment, the fiber collecting groove is filled out with a boron treatment powder. According to certain preferred embodiments, in order to apply the boron treatment powder only in the area of the fiber collecting groove and to hold it there, it is provided that the boron treatment powder is pressed into the fiber collecting groove of a rotating rotor by means of centrifugal forces. In certain preferred embodiments, the amount of the filled-in boron treatment powder is selected such that it fills out the volume of the fiber collecting groove. As a result of the rotation of the rotor, it will then be achieved that the particles of the boron treatment powder will travel exclusively into the area of the fiber collecting groove, without additional measures having to be taken.
According to advantageous features of certain preferred embodiments of the invention, in order to ensure that the boron treatment powder remains exclusively in the area of the fiber collecting groove, during an annealing process, it is provided that the boron treatment powder is held in the fiber collecting groove, during the annealing, by an insert that is placed in the rotor. It is Contemplated that this insert be a spring steel strip that is inserted into the spinning rotor, for example.
According to certain preferred embodiments of the invention, it is provided that the insert is placed in the interior of the rotor as a filler. It is contemplated that this type of a filler be introduced into the spinning rotor in a pulpy or liquid form and then hardened. A requirement of the filler is that it be made of a material that can be easily removed. For example, it is contemplated to use a molding sand such as those used in founding.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.